• Economic and Environmental Geology
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• v.50 no.6
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• pp.509-515
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• 2017

Quartz is the most abundant mineral in the Earth's continental crust. Therefore, understanding of quartz dissolution and precipitation is very important to know about weathering processes and interactions between rocks and water in hydrothermal and metamorphic environments. This paper presents a basic review on the research about quartz dissolution mechanism under various physico-chemical conditions. We rearranged the relationship between each physico-chemical factor and dissolution mechanism from the results of previous researchers in this paper. From this result, we understood that quartz dissolution and precipitation are affected by each factor such as temperature, pH, and applied stress conditions at contact point. In particular, we recognized that the high pH and temperature conditions have different anion concentrations on mineral's surface. As a result, high pH and temperature conditions have a better effect than applied stress condition to the quartz dissolution mechanism.

• Journal of Ginseng Research
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• v.39 no.4
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• pp.322-330
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• 2015

Background: UV-irradiated keratinocytes secrete various proinflammatory cytokines. UV-induced skin damage is mediated by growth factors and proinflammatory cytokines such as granulocyte macrophage colony stimulating factor (GM-CSF). In a previous study, we found that the saponin of Korean Red Ginseng (SKRG) decreased the expression of GM-CSF in UVB-irradiated SP-1 keratinocytes. In this study, we attempted to find the inhibitory mechanism of SKRG on UVB-induced GM-CSF expression in SP-1 keratinocytes. Methods: We investigated the inhibitory mechanism of SKRG and ginsenosides from Panax ginseng on UVB-induced GM-CSF expression in SP-1 keratinocytes. Results: Treatment with SKRG decreased the expression of GM-CSF mRNA and protein induced by irradiation of UVB in SP-1 keratinocytes. The phosphorylation of ERK was induced by UVB at 10 min, and decreased with SKRG treatment in SP-1 keratinocytes. In addition, treatment with SKRG inhibited the UVB-induced phosphorylation of epidermal growth factor receptor (EGFR), which is known to be an upstream signal of ERK. From these results, we found that the inhibition of GM-CSF expression by SKRG was derived from the decreased phosphorylation of EGFR. To identify the specific compound composing SKRG, we tested fifteen kinds of ginsenosides. Among these compounds, ginsenoside-Rh3 decreased the expression of GM-CSF protein and mRNA in SP-1 keratinocytes. Conclusion: Taken together, we found that treatment with SKRG decreased the phosphorylation of EGFR and ERK in UVB-irradiated SP-1 keratinocytes and subsequently inhibited the expression of GM-CSF. Furthermore, we identified ginsenoside-Rh3 as the active saponin in Korean Red Ginseng.

• Journal of Photoscience
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• v.9 no.2
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• pp.323-325
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• 2002

Bacillus Anthracis is the causative agent of anthrax. The major virulence factors are a poly-D glutamic acid capsule and three-protein component exotoxin, which is collectively known as anthrax toxin, protective antigen (PA, 83 kDa), lethal factor (LF, 90 kDa), and edema factor (EF, 89 kDa). These three proteins individually have no known toxic activities, but in combination with PA form two toxins (lethal toxin and edema toxin), causing different pathogenic responses in animals and cultured cells. However, it remains to be elucidated for pathogenic mechanism of anthrax toxin. In this study, we constructed toxin component in bacterial overexpression system and purified the native toxin from Bacillus anthracis delta sterne F32 using FPLC system. Recombinant toxin showed high homogeneity and rapid purification processes. Also, this recombinant toxin was comparable to B. anthracis native toxin in terms of cytotoxic effects on cultured cell lines.

• Bulletin of the Korean Chemical Society
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• v.24 no.1
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• pp.65-69
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• 2003

The kinetic and chemical mechanisms of AChE-catalyzed hydrolysis of short-chain thiocholine esters are relatively well documented. Up to propanoylthiocholine (PrTCh) the chemical mechanism is general acid-base catalysis by the active site catalytic triad. The chemical mechanism for the enzyme-catalyzed butyrylthiocholine(BuTCh) hydrolysis shifts to a parallel mechanism in which general base catalysis by E199 of direct water attack to the carbonyl carbon of the substrate. [Selwood, T., et al. J. Am. Chem. Soc. 1993, 115, 10477- 10482] The long chain thiocholine esters such as hexanoylthiocholine (HexTCh), heptanoylthiocholine (HepTCh), and octanoylthiocholine (OcTCh) are hydrolyzed by electric eel acetylcholinesterase (AChE). The kinetic parameters are determined to show that these compounds have a lower Michaelis constant than BuTCh and the pH-rate profile showed that the mechanism is similar to that of BuTCh hydrolysis. The solvent isotope effect and proton inventory of AChE-catalyzed hydrolysis of HexTCh showed that one proton transfer is involved in the transition state of the acylation stage. The relationship between the dipole moment and the Michaelis constant of the long chain thiocholine esters showed that the dipole moment is the most important factor for the binding of a substrate to the enzyme active site.

• Biomolecules & Therapeutics
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• v.21 no.5
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• pp.323-331
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• 2013

TGF-${\beta}$ pathway is being extensively evaluated as a potential therapeutic target. The transforming growth factor-${\beta}$ (TGF-${\beta}$) signaling pathway has the dual role in both tumor suppression and tumor promotion. To design cancer therapeutics successfully, it is important to understand TGF-${\beta}$ related functional contexts. This review discusses the molecular mechanism of the TGF-${\beta}$ pathway and describes the different ways of tumor suppression and promotion by TGF-${\beta}$. In the last part of the review, the data on targeting TGF-${\beta}$ pathway for cancer treatment is assessed. The TGF-${\beta}$ inhibitors in pre-clinical studies, and Phase I and II clinical trials are updated.

• Journal of the Korean Ceramic Society
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• v.34 no.7
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• pp.747-757
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• 1997

ZSM-5 zeolite composite membranes have been synthesized from a silica sol solution containing TPABr as an organic template by the dip-coating and the pressurized-coating hydrothermal treatment techniques. The CO2 separation efficiency of synthesized composite membranes was also investigated. The permeation mechanism of CO2 through ZSM-5 membranses was the surface diffusion, and that of N2, O2, and He gases was Knudsen diffusion or activated diffusion depending on the synthetic method of membranes and the measurement temperature. The CO2/N2 separation factor of the membrane prepared by the dip-coating hydrothermal treatment was 2.5 at about 12$0^{\circ}C$, while the ZSM-5 composite membrane synthesized by the pressurized-coating hydrothermal treatment technique showed the CO2/N2 separation factor of 9.0 at room temperature higher than that ever reported in the literature.

• Korean Journal of Clinical Laboratory Science
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• v.37 no.1
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• pp.41-46
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• 2005

It is known that mast cells (MCs) are increased in H. pylori-infected gastritis and its increase is mediated by stem cell factor (c-kit ligand). To determine the mechanism of mast cell recruitment and activation by stem cell factor, weinvestigated the expression of stem cell factor receptor (c-kit) in H. pylori-positive and -negative gastric mucosa. Biopsy specimens from 16 H. pylori-negative and 20 positive subjects were examined. H. pylori infection in gastric mucosa was examined by the Warthin-Starry method. MC and c-kit were identified by immunohistochemisty, using a monoclonal antihuman MC tryptase antibody and a polyclonal anti-human c-kit antibody. Densities of MC and c-kit positive cell were measured by a computerized image analysis system. MCs were detected in the lamina propria of both H. pylori-positive and -negative gastric mucosa. Densities of MC and c-kit positive cell were significantly greater in H. pylori-positive than -negative subjects. c-kit was located on the surface of MCs. These results indicate that stem cell factors may be one of the factors involved in mast cell increase and that they activate mast cells by binding with c-kit.

• Journal of Microbiology and Biotechnology
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• v.16 no.3
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• pp.391-398
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• 2006

$NF-{\kappa}B$ is a transcription factor involved in the innate immunity against bacterial infection and inflammation. It is also known to render cells resistant to the apoptosis caused by some anticancer drugs. Such a chemoresistance of cancer cells may be related to the activation of $NF-{\kappa}B$ transcription factor; however, the mechanism of activation is not well understood. Here, we demonstrate that a chemotherapeutic agent, etoposide, independently stimulates the $I{\kappa}B{\alpha}$ degradation pathway and PI3-kinase/Akt signaling pathway: The classical $I{\kappa}B{\alpha}$ degradation pathway leads to the nuclear translocation and DNA binding of p65 subunit through $IKK{\beta}$ kinase, whereas the PI3-kinase/Akt pathway plays a distinct role in activating this transcription factor. The PI3-kinase/Akt pathway acts on the p50 subunit of the $NF-{\kappa}B$ transcription factor and enhances the DNA binding affinity of the p50 protein. It may also explain the role of the PI3-kinase/Akt pathway in the anti-apoptotic function of $NF-{\kappa}B$ during chemoresistance of cancer cells.

• Environmental Engineering Research
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• v.25 no.3
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• pp.439-445
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• 2020

In the estimation of the aerosol single fiber efficiency using fibrous filters, there is a size range, where the particles penetrate most effectively through the fibrous collectors, and corresponding minimum single fiber efficiency. For small particles in which the diffusion mechanism is dominant, the Cunningham slip correction factor (C_c) affects the single fiber efficiency and the most penetrating particle size (MPPS). Therefore, for accurate estimation, C_c is essential to be considered. However, many previous studies have neglected this factor because of its complexity and the associated difficulty in deriving the appropriate parameterization particularly for the MPPS. In this study, the expression for the MPPS, and the corresponding expression for the minimum single fiber efficiency are analytically derived, and the effects of C_c are determined. In order to accommodate the slip factor for all particle-size ranges, C_c is simplified and modified. Overall, the obtained analytical expression for the MPPS is in a good agreement with the exact solution.

• Journal of Photoscience
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• v.9 no.2
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• pp.243-245
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• 2002

Pigment-dispersing factor (PDF) is an octadecapeptide distributed in the optic lobe and the brain in a variety of insect species. There are lines of evidence suggesting possible involvement of PDF in the insect circadian system. However, its physiological roles in the circadian time keeping mechanism have not been clearly defined. In this study, we have examined the phase shifting effects of Gryllus-PDF on the circadian locomotor rhythm in the cricket Gryllus bimaculatus of which circadian clock is located in the optic lobe. Phase shifts in the circadian activity rhythm were measured following microinjection of 22nl of vehicle (Ringer's solution) or O.lmM PDF into the optic lobe through the compound eye at various circadian times. The results showed that PDF induced phase shifts of the circadian clock in a phase-dependent manner, suggesting that it may play a role as an input signal for the circadian clock.